The invention relates to a device for turning or reversing flat copies in half-revolution sheet-processing machines, such as rotary printing machines.
The published German Patent Document DE 37 10 257 A1 is concerned with a sheet-fed rotary printing machine for performing single-sided multicolored printing or first form and perfecter printing, also known as recto/verso printing. A sheet transfer drum is accommodated between sheet-carrying cylinders of two printing units, which are disposed in a travel direction of sheet material; according to the proposal in this document, in order to achieve a construction which, in particular, operates independently of format, the transfer nip between the sheet transfer cylinder and the impression cylinder of the second printing unit is enlarged in comparison with the normal nip width to the impression cylinder of the first printing unit, and the clear interspace is bridged by a gripper system that is movable out of the circumference of the sheet transfer cylinder in order to grip the sheet leading or trailing edge.
The published German Patent Document DE 37 17 093 A1 is also concerned with a rotary printing machine for recto and recto/verso printing. Arranged between the impression cylinders of two printing units, in the travel direction of the sheet, is a sheet transfer cylinder, all of the cylinders having gripper systems assigned thereto. In order to achieve a construction with increased transfer reliability, even in the case of very thick printing material, a sheet feeder arranged downline from the sheet transfer cylinder is provided with a feeder top side configured at least approximately flat and extending somewhat tangentially to the sheet transfer cylinder. While the grippers of the sheet transfer cylinder holding the sheet trailing edge approach the feeder top side, the cylinder pushes the sheet onto the feeder top side with the free sheet leading edge in front, the sheet being lifted by the sheet transfer cylinder off the feeder top side by the trailing edge of the sheet.
The proposed embodiments outlined above are subject to the disadvantage that the sheet material necessarily rests with the respectively freshly printed side thereof on the outer surface of the transfer drum (storage drum) and is tensioned in order to achieve in-register turning or reversing. Damage to the printed image results from this unavoidable relative movement between the drum outer cylindrical surface or jacket and the sheet.
The published German Patent Document DE 196 15 730 A1 is concerned with a turning or reversing device for a printing machine, in particular to a sheet-fed rotary offset printing machine. The turning or reversing device for a printing machine comprises a transfer drum arranged between a first impression cylinder and a second impression cylinder. Below the transfer drum is a register cylinder having a large number of suction openings for holding the sheet by suction; after the gripper device has opened, the register cylinder conveys the sheet in-register into a temporary storage system. In the latter, the sheet is stored temporarily, in an approximately stretched-out form, on a first sheet guide device provided with blower or blast nozzles. A tongs-type turning or reversing gripping device arranged on the transfer drum grips the trailing edge of the sheet deposited in the temporary storage system, and transfers the edge to a conventional gripper device formed on the downline impression cylinder, which then supplies the sheet turned or reversed in this manner to a downline printing nip in order to print the underside of the sheet.
A disadvantage of this method is that operations are not performed with simultaneous gripper closure on the leading and trailing edge of the sheet.
In addition to the possible embodiments outlined from the prior art, the sheet material can also be stored on the impression cylinder. Following printing, the sheet material is stored on the impression cylinder, subsequently gripped by the gripper systems of the transfer drum, and turned or reversed. With regard to the half-revolution machine concept, i.e., constructing the cylinder with twice the circumference of that of the impression cylinder, the printing operation is completed, i.e., the sheets are printed out until, in recto printing mode, the leading edge thereof is transferred to the following transfer drum. For this reason, it is necessary to provide a complete sheet length between the printing point and transfer center line. Should it be possible for the sheet material to be turned or reversed, a further sheet-length space must be provided under the impression cylinder in order to store the sheet.
Reserving a further sheet-length space underneath the impression cylinder necessarily results in a specific relative arrangement of transfer cylinders, i.e., blanket cylinder, impression cylinder and transfer drum, relative to one another. If the necessary installation space upline from the printing point is to remain for the sheet guiding elements necessary to ensure the print quality, a large cylinder diameter is required in relation to the maximum Printing-material length. This entails higher production and manufacturing costs, greater dynamic problems due to the higher masses to be moved and, overall, an increase in the length of printing machines which, in print shops, occupy adjusting or installation area which is tight in any case.
A common factor in all of the heretofore proposed constructions is that they require a different configuration of the transfer drum in the turning or reversing printing unit compared with the configuration of the transfer drum in the other printing units. This results in considerable problems in the recto printing mode, wherein a multicolor rotary printing machine is also intended to be operated, in particular when processing a relatively stiff printing material such as pasteboard or cardboard.
Starting from the prior art outlined hereinabove, it is an object of the invention to provide a device for reversing flat copies in half-revolution sheet-processing machines, the device utilizing simultaneous gripper closure of the sheet material at the leading and trailing edge of the respective sheets, and operating with the greatest accuracy.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, in a sheet-processing rotary printing machine operatable in recto printing and recto/verso printing modes, a device for reversing sheets, comprising a transfer drum bounded by two sheet-guiding cylinders, a reversing/storage drum and an additional transport element assigned to the transfer drum, the transfer drum being drivable in opposite directions of rotation in the recto printing and the recto/verso printing modes, and gripper systems actable in both directions of rotation of the transfer drum, the gripper systems being in accommodated on an imaginary jacket surface of the transfer drum.
In accordance with another feature of the invention, the reversing/storage drum and the additional transport element, in the recto printing mode, are located outside a transport path of a sheet on the sheet-guiding cylinders.
In accordance with a further feature of the invention, a transport path of a sheet, in the recto/verso printing mode, is located on a side of a jacket surface of the transfer drum, which is located opposite the transport path of the sheet in the recto printing mode.
In accordance with an added feature of the invention, the transfer drum has a contour set back with respect to an enveloping curve of the gripper systems.
In accordance with an additional feature of the invention, the reversing/storage drum and the additional transport element are driven only in the recto/verso printing mode, and are stopped in the recto printing mode.
In accordance with yet another feature of the invention, the sheet-reversing device includes a first one of the sheet-guiding cylinders, the transfer drum drivable in a direction opposite to the direction of rotation of the recto printing mode, the reversing/storage drum and the additional transport element engaging with the second one of the sheet-guiding cylinders serve for transporting and reversing the sheet in the recto/verso printing mode.
In accordance with yet a further feature of the invention, in the recto/verso printing mode, the transport path of the sheet is over a first one of the sheet-guiding cylinders, a single-revolution transfer cylinder, the transfer drum drivable in a direction opposite to the direction of rotation of the recto printing mode, and the additional transport element functioning as a reversing drum.
In accordance with yet an added feature of the invention, in the recto/verso printing mode, the transport path of the sheet extends from a first one of the sheet-guiding cylinders over a storage drum, the transfer drum functioning as a reversing drum, over the additional transport element to the jacket surface of a second one of the sheet-guiding cylinders.
In accordance with yet an additional feature of the invention, a first one of the sheet-guiding cylinders, the transfer drum and a second one of the sheet-guiding cylinders are constructed as half-revolution cylinders.
In accordance with still another feature of the invention, the reversing/storage drum and the additional transport element are constructed by a technique selected from the group thereof consisting of a single revolution and a division by integers in relation to the diameter of a printing-form cylinder.
In accordance with still a further feature of the invention, the gripper systems act on both sides on the transfer drum, and are formed as tongs-type gripper systems for executing a 180xc2x0 pivoting movement.
In accordance with still an added feature of the invention, the gripper systems act on both sides on the transfer drum and are formed, respectively, as a double gripper with two gripper fingers drivable about a common shaft.
In accordance with still an additional feature of the invention, the gripper systems act on both sides on the transfer drum and are formed, respectively, as a cam-controlled, vertically displaceable T-shaped gripper to which two gripper pad surfaces are assigned.
In accordance with another feature of the invention, the respective gripper system on the transfer drum is formed as a gripper system which is activatable in the recto printing mode, and is settable into a dipped position in the recto/verso printing mode.
In accordance with a further feature of the invention, the respective gripper system of the transfer drum is formed as a folding gripper system which is pivotable about a pivot shaft.
In accordance with an added feature of the invention, a supporting element having an inclined contact face is accommodated on at least one of the transfer drum and the additional transport element, and including a catching element activatable for setting relatively stiff sheet material against the supporting element.
In accordance with an additional feature of the invention, the relatively stiff sheet material is transferrable by the catching device from a stretched position into a wound-up position on the supporting element.
In accordance with yet another feature of the invention, in the recto printing mode, a drive to one of the sheet-guiding cylinders is provided via a gear train.
In accordance with yet a further feature of the invention, in the recto/verso printing mode, a drive to the other of the sheet-guiding cylinders is provided via another gear train having a coupling element.
In accordance with another aspect of the invention, there is provided a printing unit for reversing sheet material, comprising a transfer drum bounded by two sheet-guiding cylinders, a reversing/storage drum and an additional transport element assigned to the transfer drum, the transfer drum being drivable in opposite directions of rotation in recto printing and recto/verso printing modes, and gripper systems actable in both directions of rotation of the transfer drum, the gripper systems being accommodated on an imaginary jacket surface of the transfer drum.
In accordance with a concomitant aspect of the invention, there is provided a multicolor rotary printing machine having a device for reversing sheets, comprising a transfer drum bounded by two sheet-guiding cylinders, a reversing/storage drum and an additional transport element assigned to the transfer drum, the transfer drum being drivable in opposite directions of rotation in recto printing and recto/verso printing modes, and gripper systems actable in both directions of rotation of the transfer drum, the gripper systems being accommodated on an imaginary jacket surface of the transfer drum.
The advantages of the invention are primarily to be seen in the fact that the shaping of the sheet-guiding cylinder functioning as a transfer drum in the reversing printing unit is identical to that of the transfer drum in an exclusively recto printing unit. Thus, the sheet transfer path in the recto printing mode of the rotary printing machine lies outside all the components required to reverse or turn the sheet. The transport path of the sheet material, whether it is paper of any grammage or else relatively stiff cardboard or pasteboard, in the recto/verso printing mode of the reversing printing unit is located on the opposite side of the sheet-guiding cylinder functioning as a transfer cylinder. The transfer drum, which has a direction of rotation, for example, in the recto printing mode corresponding to the clockwise direction, is operated in a counterclockwise direction of rotation in the recto/verso printing mode and comprises gripper systems which act on both sides, so that sheet material can be fixed to the transfer drum in one and the other direction of rotation.
In further refinement of the idea upon which the invention is based, the reversing/storage drum and an additional transport element can be arranged outside the transport path of the sheet material on the sheet-guiding cylinder in the recto printing mode. The result, therefore, even in the reversing printing unit in the recto printing mode of the rotation, is a sheet passage which corresponds to the greatest extent to the sheet run through a pure recto printing unit, so that, in the recto printing mode, the reversing printing unit is printed with the same high quality standard as pure recto printing units.
The transport path of the sheet material in the recto/verso printing mode is provided on the side of the jacket surface of the transfer drum between the sheet-guiding drums, the side being opposite the transport path of the sheet in the recto printing mode. By configuring the transfer drum as a cylinder that can be driven in both directions of rotation, the sheet transport path in the recto printing mode can be decoupled strictly from the sheet transport path in recto/verso printing mode. In order to achieve collision-free transport, even of relatively stiff printing material, through the reversing printing unit configured in accordance with the invention, the contour of the transfer drum is configured so as to be set back in relation to the gripper systems accommodated on the outer or jacket surface thereof, so that the diversion and secure storage of the sheet material to be reversed or turned is ensured on the transfer drum during the reversing or turning action.
With the configuration of a reversing or turning printing unit proposed in accordance with the invention for a sheet-processing rotary printing machine, reversing/storage drums and an additionally arranged transport element can be driven only in the recto/verso operating mode, while in pure recto printing operation of the reversing printing unit these components can be stopped. As a result, firstly drive power can be saved, and secondly the pure recto printing operation of a reversing printing unit configured in accordance with the invention is not influenced by components required for the recto/verso mode.
In the recto/verso printing mode, the transport path of the sheet material, whether the printing material is in paper form of lighter or heavier grammages, or printing material in the form of relatively stiff cardboard or pasteboard, and the reversing or turning thereof, can run over a first sheet-guiding cylinder, a transfer cylinder rotating in a direction opposite to the direction of rotation of the recto printing mode, and over a reversing drum and the additional transport unit, which can likewise be of cylindrical configuration, and run to the second sheet-guiding cylinder. In the recto/verso printing mode of the reversing printing unit proposed in accordance with the invention, a further transport path can run over the first sheet-guiding cylinder; can further run over a single-revolution transfer cylinder and over the transfer drum rotating in the direction opposite to the direction of rotation in the recto printing mode, through an additional transport cylinder functioning as a reversing drum in this alternative embodiment. Furthermore, a further transport possibility for the sheet material in the recto/verso printing mode is provided by the transport of the sheet from the first sheet-guiding cylinder to a storage drum, from there to a transfer drum functioning as a reversing drum, from this to an additional transport element, which can likewise be of cylindrical configuration, to the outer or jacket surface of the second sheet-guiding cylinder.
In order to achieve identical guidance of the sheet material, whether it is paper of lighter and heavier grammages or relatively stiff cardboard or pasteboard, through the pure recto printing units and the reversing printing unit configured in accordance with the invention, the first sheet-guiding cylinder, the transfer drum and the second sheet-guiding cylinder are preferably constructed as half-revolution cylinders, i.e., with twice the diameter in comparison with the printing-form cylinder.
Reversing/storage drums and the additional transport element, likewise of cylindrical configuration, may therefore be constructed with single revolution or with an integer divider in relation to the diameter of the printing form cylinder. This is economical with respect to installation space and is not critical with respect to the yet unprinted side of the sheet material, because no smearing phenomena can occur.
Accommodated on the transfer drum bounded in the reversing printing unit by two half-revolution sheet-guiding cylinders are gripper systems acting on both sides which, in one alternative configuration are tongs-type grippers and are able to carry out a pivoting movement covering about 180xc2x0. In addition to a tongs-type gripper carrying out a 180xc2x0 pivoting movement, the gripper systems that act on both sides on the transfer drum can also be constructed as double grippers with two mutually opposed gripper arms which can be driven separately on a common axis. The gripper fingers of the double gripper cooperate, respectively, with a separate gripper pad surface. In addition, it is conceivable to construct the gripper system acting on both sides on the outer or jacket surface of the transfer drum also as cam-controlled T-shaped grippers which can be displaced vertically up and down, with which likewise two mutually separate gripper pad surfaces can be associated. The vertical movement of the T-shaped gripper on the outer or jacket surface of the transfer drum may be implemented, for example, by a lever transmission performing a pivoting movement about a fixed bearing, which can be generated by a roller/cam drive.
In order to avoid collisions with other machine components, the gripper systems of the transfer drum proposed in accordance with the invention in the reversing printing unit may be configured as systems which can be activated in recto printing mode, i.e., can be extended, and with gripper systems which can be set into a dipped position in the recto/verso operating mode. To this end, the gripper systems on the outer or jacket surface of the transfer drum can be constructed so that they can be retracted as a whole into the outer or jacket surface of the transfer drum; finally, it is also possible to configure the gripper fingers about a pivot axis so that a folding movement describing a 180xc2x0 circular arc is possible.
With all the gripper systems described hereinbefore, reverse acceleration of the sheet material, whether it is paper or relatively stiff cardboard or pasteboard, can be carried out over an extended time period, because the transport path of the sheet material runs without collision as a secant through the theoretical gripper circle, i.e., the enveloping curve of the transfer drum and of the additional transport element. Inherent in this alternative embodiment of the sheet material during reversing or turning is a considerably gentler accelerating action; a further positive side effect of this guidance of the sheet material during turning or reversing is the achievement of higher speeds in the recto/verso printing mode of the multicolor rotary printing machine equipped with the reversing or turning printing unit configured in accordance with the invention. The described gripper systems dip into the circular contour of the transfer drum when in a position in relation to the two adjacent cylinders, wherein a collision is threatened.
In a preferred alternative embodiment of the transfer drum and/or of the additional transport element within the reversing printing unit, a conical support can be fitted both to the transfer drum and to the additional transport element, with which in particular the side edges of relatively stiff cardboard or pasteboard material can be supported. By catching devices cooperating with the supporting element having conical supporting surfaces, relatively stiff sheet material can be pressed against the contact surfaces of the conical supporting elements, in order to counteract excessive stretching and therefore the risk of collision with the next sheet stored on a cylinder. By the activatable catching hooks, in particular the trailing edge of relatively stiff cardboard or pasteboard materials is held on the radius of the cylinder, i.e., brought from a stretched position effected by the stiffness inherent in this printing material into a wound-up position, i.e., a slightly curved position set against the outer or jacket surface. The supporting element arrangement, having inclined supporting surfaces, can be used as well on the transfer drum; in another alternative embodiment, the additional transport element, with a reduced diameter due to the installation space, can be provided with a device that influences the stretched position of relatively stiff material.
On the reversing printing unit configured in accordance with the invention, both a gear train for the recto printing mode and a gear train for the recto/verso printing mode are provided. In the recto printing mode, the drive to the second sheet-guiding cylinder is provided via a first gear train, from which the gears of the reversing drum and of the additional transport element are disengaged. In the recto/verso printing mode, the drive to the second sheet-guiding cylinder is provided via a gear train lying parallel with the first gear train, wherein the drive from the first sheet-guiding cylinder is transferred, for example, via the gear driving the reversing drum, to a further gear mounted on the shaft of the transfer drum, and therefrom to the gear of the additional transport element which, in turn, drives the drive gear of the second sheet-guiding cylinder. All the shafts of the foregoing cylinders are mounted with low friction in rolling-contact bearings in the side walls of the reversing or turning printing unit. In order to shift or change the gear trains over in accordance with the selected operating mode of the reversing or turning printing unit, a coupling element or clutch is provided in the gear train, preferably on the shaft of the transfer drum, with which the changeover from the recto printing mode to the recto/verso printing mode can be performed by coupling between direct and indirect drive via the reversing or turning drum on the transfer drum. At the same time, assurance is offered that simultaneous rotation of the driving systems in relation to one another is carried out in such a manner that the reversing drum grips the end of the sheet lying on the impression cylinder precisely as a function of the format. In the recto printing mode, the changeover is effected so that the verso printing components in a rest position of the reversing drum and additional transport system are separated, and the transfer drum is coupled directly into the drive train in synchronism with the impression cylinder grippers.
The configuration of a reversing printing unit proposed in accordance with the invention is preferably used in multicolor rotary printing machines wherein, depending upon the alternative construction of the sheet-processing machine, a number of pure recto printing units is present, and the reversing printing unit, wherein the pure recto printing operation and the recto/verso printing operation are possible, is connected therebetween. By virtue of the compatibly constructed cylinder diameters, the sheet material to be processed undergoes sheet guidance in the reversing printing unit configured in accordance with the invention when in the recto printing mode, this sheet guidance corresponding to the greatest possible extent to the sheet guidance in pure recto printing units. Due to the separation of the transport paths of the sheet material, in the pure recto printing mode, from the transport path of the sheet material, in the recto/verso printing mode, in the reversing printing unit configured in accordance with the invention, mutual influences in the operating modes are ruled out.
In the recto printing operation, the transport of the sheet material that is not to be reversed is carried out via an optimized transfer drum, whereas, when a changeover or shift is made to the recto/verso printing mode, the cylinder components best suited for this operating mode are connected together.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a device for reversing or turning flat copies in half-revolution sheet-processing machines, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: